Continuous beamforming for a MIMO-OFDM system

Abstract

A transmitting entity performs spatial processing on data symbols for each subband with an eigenmode matrix, a steering matrix, or an identity matrix to obtain spatially processed symbols for the subband. The data symbols may be sent on orthogonal spatial channels with the eigenmode matrix, on different spatial channels with the steering matrix, or from different transmit antennas with the identity matrix. The transmitting entity further performs beamforming on the spatially processed symbols, in the frequency domain or time domain, prior to transmission from the multiple transmit antennas. A receiving entity performs the complementary processing to recover the data symbols sent by the transmitting entity. The receiving entity may derive a spatial filter matrix for each subband based on a MIMO channel response matrix for that subband and perform receiver spatial processing for the subband with the spatial filter matrix.

What is claimed is: 
     
       1. A method for receiving data in a multiple-input and multiple-output communication system, comprising:
 receiving a multiple-input and multiple-output pilot; 
 determining an effective multiple-input and multiple-output channel response based on estimated initial effective multiple-input and multiple-output channel response that is based on the multiple-input and multiple-output pilot; and 
 performing receiver spatial processing on received symbols for a symbol period with the determined effective multiple-input and multiple-output channel response to recover data symbols. 
 
     
     
       2. The method of  claim 1 , wherein the data received comprises data symbols for each frequency subband that have been spatially processed with an eigenmode matrix. 
     
     
       3. The method of  claim 1 , wherein the data received comprises data symbols for each frequency subband that have been spatially processed with a steering matrix. 
     
     
       4. The method of  claim 1 , wherein the data received comprises data symbols for each frequency subband that have been spatially processed with an identity matrix. 
     
     
       5. The method of  claim 1 , wherein the data received was transmitted using beamforming in the frequency domain. 
     
     
       6. The method of  claim 1 , wherein the data received was transmitted using beamforming in the time domain. 
     
     
       7. The method of  claim 1 , wherein the data received was transmitted without beamforming. 
     
     
       8. The method of  claim 1 , wherein performing receiver spatial processing on received symbols comprises performing minimum mean square error spatial processing for each subband. 
     
     
       9. The method of  claim 8 , wherein performing minimum mean square error spatial processing comprises:
 deriving a spatial filter matrix for each subband to obtain symbol estimates; and 
 multiplying the symbol estimates with a scaling matrix to obtain normalized estimates of the data symbols. 
 
     
     
       10. The method of  claim 1 , wherein performing receiver spatial processing on received symbols comprises performing channel correlation matrix inversion for each subband. 
     
     
       11. A wireless device in a multiple-input and multiple-output communication system, comprising:
 a processor; 
 memory in electronic communication with the processor; 
 instructions stored in the memory, the instructions being executable by the processor to:
 receive a multiple-input and multiple-output pilot; 
 determine an effective multiple-input and multiple-output channel response based on an estimated initial effective multiple-input and multiple-output channel response that is based on the multiple-input and multiple-output pilot; and 
 perform receiver spatial processing on received symbols for a symbol period with the determined effective multiple-input and multiple-output channel response to recover data symbols. 
 
 
     
     
       12. The wireless device of  claim 11 , wherein the data received comprises data symbols for each frequency subband that have been spatially processed with an eigenmode matrix. 
     
     
       13. The wireless device of  claim 11 , wherein the data received comprises data symbols for each frequency subband that have been spatially processed with a steering matrix. 
     
     
       14. The wireless device of  claim 11 , wherein the data received comprises data symbols for each frequency subband that have been spatially processed with an identity matrix. 
     
     
       15. The wireless device of  claim 11 , wherein the data received was transmitted using beamforming in the frequency domain. 
     
     
       16. The wireless device of  claim 11 , wherein the data received was transmitted using beamforming in the time domain. 
     
     
       17. The wireless device of  claim 11 , wherein the data received was transmitted without beamforming. 
     
     
       18. The wireless device of  claim 11 , wherein the instructions executable to perform receiver spatial processing on received symbols comprises instructions executable to perform minimum mean square error spatial processing for each subband. 
     
     
       19. The wireless device of  claim 18 , wherein the instructions executable to perform minimum mean square error spatial processing comprises instructions executable to:
 derive a spatial filter matrix for each subband to obtain symbol estimates; and 
 multiply the symbol estimates with a scaling matrix to obtain normalized estimates of the data symbols. 
 
     
     
       20. The wireless device of  claim 11 , wherein the instructions executable to perform receiver spatial processing on received symbols comprises instructions executable to perform channel correlation matrix inversion for each subband. 
     
     
       21. An apparatus configured for receiving data in a multiple-input and multiple-output communication system, comprising:
 means for receiving a multiple-input and multiple-output pilot; 
 means for determining an effective multiple-input and multiple-output channel response based on an estimated initial effective multiple-input and multiple-output channel response that is based on the multiple-input and multiple-output pilot; and 
 means for performing receiver spatial processing on received symbols for a symbol period with the determined effective multiple-input and multiple-output channel response to recover data symbols. 
 
     
     
       22. The apparatus of  claim 21 , wherein the data received comprises data symbols for each frequency subband that have been spatially processed with an eigenmode matrix. 
     
     
       23. The apparatus of  claim 21 , wherein the data received was transmitted using spatial processing of the data symbols for each frequency subband with a steering matrix. 
     
     
       24. The apparatus of  claim 21 , wherein the data received comprises data symbols for each frequency subband that have been spatially processed with an identity matrix. 
     
     
       25. The apparatus of  claim 21 , wherein the data received was transmitted using beamforming in the frequency domain. 
     
     
       26. The apparatus of  claim 21 , wherein the data received was transmitted using beamforming in the time domain. 
     
     
       27. The apparatus of  claim 21 , wherein the data received was transmitted without beamforming. 
     
     
       28. The apparatus of  claim 21 , wherein performing receiver spatial processing on received symbols comprises performing minimum mean square error spatial processing for each subband. 
     
     
       29. The apparatus of  claim 28 , wherein the means for performing minimum mean square error spatial processing comprises:
 means for deriving a spatial filter matrix for each subband to obtain symbol estimates; and 
 means for multiplying the symbol estimates with a scaling matrix to obtain normalized estimates of the data symbols. 
 
     
     
       30. The apparatus of  claim 21 , wherein performing receiver spatial processing on received symbols comprises performing channel correlation matrix inversion for each subband. 
     
     
       31. A computer-program product for receiving data in a multiple-input and multiple-output communication system, the computer-program product comprising a non-transitory computer-readable medium having instructions thereon, the instructions comprising:
 code for causing a wireless device to receive a multiple-input and multiple-output pilot; 
 code for causing the wireless device to determine an effective multiple-input and multiple-output channel response based on an estimated initial effective multiple-input and multiple-output channel response that is based on the multiple-input and multiple-output pilot; and 
 code for causing the wireless device to perform receiver spatial processing on received symbols for a symbol period with the determined effective multiple-input and multiple-output channel response to recover data symbols. 
 
     
     
       32. The computer-program product of  claim 31 , wherein the data comprises data symbols for each frequency subband that have been spatially processed with an eigenmode matrix. 
     
     
       33. The computer-program product of  claim 31 , wherein the data received comprises data symbols for each frequency subband that have been spatially processed with a steering matrix. 
     
     
       34. The computer-program product of  claim 31 , wherein the data received comprises data symbols for each frequency subband that have been spatially processed with an identity matrix. 
     
     
       35. The computer-program product of  claim 31 , wherein the data received was transmitted using beamforming in the frequency domain. 
     
     
       36. The computer-program product of  claim 31 , wherein the data received was transmitted using beamforming in the time domain. 
     
     
       37. The computer-program product of  claim 31 , wherein the data received was transmitted without beamforming. 
     
     
       38. The computer-program product of  claim 31 , wherein the code for causing the wireless device to perform receiver spatial processing on received symbols comprises code for causing the wireless device to perform minimum mean square error spatial processing for each subband. 
     
     
       39. The computer-program product of  claim 38 , wherein the code for causing the wireless device to perform minimum mean square error spatial processing comprises:
 code for causing the wireless device to derive a spatial filter matrix for each subband to obtain symbol estimates; and 
 code for causing the wireless device to multiply the symbol estimates with a scaling matrix to obtain normalized estimates of the data symbols. 
 
     
     
       40. The computer-program product of  claim 31 , wherein the code for causing the wireless device to perform receiver spatial processing on received symbols comprises performing channel correlation matrix inversion for each subband.